Ignition system



Aug. 12, 1958, y B. H. SHORT ETAL IGNITION SYSTEM Filed Jan. 26, 1956Fla/e Arrae/vm United States Patent() IGNITION SYSTEM Brooks H. Shortand Harry E. Freeman, Anderson, Ind., assignors to General MotorsCorporation, Detroit, Mich., a corporation of Delaware ApplicationJanuary 26, 1956, Serial No. 561,487

9 Claims. (Cl. 123179) This invention relates to ignition systems forinternal combustion engines and is more particularly concerned with animproved circuit for causing an electronic switch in an ignition circuitto become conductive.

It is an object of the present invention to increase the voltage of acircuit which controls the triggering of an electronic switch in anignition circuit for an internal combusition engine during the periodswhen the starting motor for the engine is energized.

It is another object of the present invention to control the triggeringof an electronic switch in an ignition system for an internal combustionengine by a circuit that includes a transformer that has one windingconnected with the electronic switch and the other winding connected tothe source of current for the ignition system.

A further object of the present invention is to control the conductivityof an electronic switch in an ignition system for an internal combustionengine by a circuit that includes a transformer that has its secondarywinding connected to the electronic switch and its primary windingconnected in circuit with a pair of breaker points and with the sourceof current for the ignition system.

A still further object of the present invention is to provide anelectronic ignition system for an internal combusition engine with acontrol circuit that is energized by a low voltage from the source ofpower for said electronic ignition system, which control circuitincludes a transformer that has its secondary winding connected with anelectronic switch and its primary winding connected in circuit with apair of breaker points and a voltage divider which has provisions forchanging its ratio so the voltage supplied to the transformer primary ismaintained substantially constant even through the voltage at saidsource is decreased when the starting circuit for the engine isenergized.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawing wherein a preferred embodiment of the present invention isclearly shown.

In the drawing, the single figure shows a wiring diagram of an ignitionsystem for an internal combustion engine according to the presentinvention.

In the drawing, the numeral 20 designates a storage battery which hasone terminal connected to ground 22 and the other terminal connected toa suitable ignition and starter switch 24 which may be of the typedisclosed in U. S. Patent 2,655,570, Brown et al., which has beenassigned to the assignee of the present invention. The switch 24 isarranged to either close the ignition circuit only or simultaneouslyclose the circuits to both the ignition and the starting motor circuits,which will be hereinafter described, or may break the starting motorcircuit and maintain the ignition circuit or may break both circuits.Obviously, two switches may be used instead of the single switch 24 and,when so used, the two switches will individually control the startingand ignition circuits.

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The starting motor circuit includes a solenoid switch 26 which has itsactuating winding 28 circuit controlled by the switch 24. When thewinding 28 is energized, the solenoid armature 30 is moved to directlyconnect the starter 32 with the battery 20. When the armature 30 closesthe starting motor 32 circuit, it also, through contact 34, closes acircuit to the windings of solenoids 36 and 38, the function of whichwill be later set forth.

The primary circuit ignition system shown includes; a vibratory coil 40,a transformer 42, a condenser 43, a pair of rectifier tubes 44 and 46, acold cathode tube 48, an inductance 50, a condenser 52, the primarywinding 53 of an ignition coil 54, a reverse tube 56 and a triggeringtube 58. The secondary ignition circuit includes the secondary winding60 of the ignition coil 54, a distributor, not shown, and spark plugsdiagrammatically shown as 62 on the drawing. The ignition system, ifdesired, may include a ballast lamp 64 and the solenoid 36, which isused to increase the voltage impressed on the ignition system duringperiods when the engine starter 32 is energized. The solenoid 36, whenused, is suitably connected to the taps of the transformer 42 as shown.The condenser is a feed through condenser and is included to reduceinterference with surrounding radio or other similar electricalequipment.

The connections and functions of resistances 66, 68 and '70 andcondensers 43, 72, 74, 76 and 78 as well as the functions and operationsof the ballast lamp 64 and use of the solenoid 36 to control the taps oftransformer 42 are all set forth in application, S. N. 402,910, filedJanuary 8, 1954, by Brooks H. Short, who has assigned the application tothe assignee of the present invention. This application also clearlydiscloses how the various heretofore mentioned parts of the primary andsecondary ignition systems are interconnected and their operation in thesystems.

The present invention is directed to a means or system for controllingthe triggering or conductivity of the triggering tube 58 so that thecondenser 52 will discharge through the primary winding 53 of coil 54.This will cause the spark plugs to ignite as is well known to thoseskilled in the art. The control circuit or means for the tube 58includes a resistance 80, a transformer 82, a potentiometer resistor 85,solenoid 38, breaker points 84, condenser 86 and battery 20.

The secondary winding 88 of the transformer 82 has one end connectedthrough resistance 80 with the grid 98 of tube 58. The other end ofwinding 88 is connected to ground 22. The primary winding 92 oftransformer 82 has one of its ends connected with the armature 94 ofsolenoid 38 and the other end connected through breaker points 84 toground 22. The condenser 86 is connected across points 84 to minimizearcing between the points 84 as they open and close.

The armature 94 of the solenoid 38 is normally held by spring 96 toengage contact 98 and complete a circuit with tap 100 of thepotentiometer resistance 85. The armature 94 is moved, when the coil ofthe solenoid is energized, to engage the contact 102 which is connectedwith tap 104 of the potentiometer resistance or voltage divider 85. Theresistance preferably has a total value of 15 ohms and the taps and 104divide the potentiometer resistance 84 into three sections 106, 108 and110 which, preferably and respectively, have values of 2, 6 and 7 ohms.The free end of section 110 is directly connected through fuse 112 andthe ignition switch 24 to the battery 20. The free end of section 106 isconnected to ground 22. The resistance 80 preferably has a value of 330Kohms.

With the above circuit arrangement in mind, the operation of thetriggering of tube 58 Will now be described.

Every time the firing of spark plug 62 is required, the secondarywinding 88 of transformer 82 supplies a positive voltage pulse to thegrid 90 of tube 58 through the resistance 80. This positive voltagepulse will cause the tube-58 tobe conductive so that condenser 52discharges.

Whenthe breaker points '84 close, current will flow throughtheprimary-Winding-92 of the transformer 82. This current will build up along anexponential curve, and will store energy in the magnetic fieldsurrounding both windings of transformer '82. At the instant ignitionis-req-uired,-the contactpoints84-open. This action causes a relativelyhigh voltage to be, developed in the primary 9 2"oftr-ansformer 82; Thisvoltage is further stepped up inthe properqphase so that the opening ofcontact points 84 results ina'higher voltage of positive polaritywithrespect to-ground ,to appear at the ungrounded terminal of secondarywinding 88. This high voltage is transferred through resistor 80.to thegrid 90 of controlled tube '58 and causes tube '58 to become ionized,thereby permitting the energy which previously had been stored incondenser 52 to be discharged through the primary 53 of ignition coil54. When the transient voltage disappears from the secondary 88,the-grid 90 of tube 58 again assumes the potential of ground 22, therebyextinguishing the'tube 58-.

Since the tube58 may be adversely affected by negative potential at thegrid 90, the entire triggering circuit has been arranged with thevoltage divider so that the voltage produced at the ungrounded terminalof secondary Winding 88 is of negligible value at the instant points 84close for the establishment of the magnetic field in the winding82.

As has'been previously pointed out, solenoids 36 and 3 8 are bothenergized when the starter solenoid 26 is energized. The energization ofsolenoid 36 will cause higher voltage to beimpressedacross the primaryignition circuits during the, periods when the starter 32 is eneri Qd.This result'is clearly set forth in the Short application supra.

When thesolenoid 3 8 is energized, the armature 94 will be movedfromitsengagement with. contact 98 into engagement with contact 102 .sothat the division ratio ofthedivider is changed from to This increasingdivision ratio when coupled with the decreasing battery voltage duringcranking, resultsin sufiicient energy and YQltagefor triggering thegrid90 of tube 58 during the ran ing p iod- While the embodiment of thepresent invention as herein disclosed constitutes apreferred form, it isto be understood that other forms might be adapted.

What is claimedisas follows:

1, In anignition; system for an internal combustion engine having; asource of D. C. current and voltage, a means for increasing the voltageof said source to a higher voltage, aload connectable to said source fordecreasing the voltage of said source, a primary circuit connected withsaid higher voltage means, and an electronic switch connected in saidprimary circuitfor controlling current fiow in said primary circuit fromsaid higher voltage means, means including a transformer having .aprimary winding connected in ,circuit with said sourcelower means and asecondary winding connected with said electronic switch for controllingcurrent flow through saidswitch and a means in the circuit between thesource and primary winding for increasing the voltage across theprimarywinding when the load is connected to said source.

.2. In an ignition system of the character described whereinanelectronic switchcontrols the flow of current from a D. C. sourcethrough a primary ignition circuit, ameansfor controlling the operationof the electronic switch, comprising in combination; a set of breakerpoints, and atransformer havingaprimary winding connected in circuitwith said source. breaker points and a secondary s winding connected incircuit with said electronic switch and means for increasing the voltageacross the primary winding when a load is connected to said source.

3. In an ignition system of the character described wherein anelectronic switch is used to control the flow of current from a D. C.current source through a primary ignition circuit, the combinationcomprising; a set of breakerpoints, a transformer having a primarywind-ing connected in circuit between said source and breaker points anda secondary winding connected in circuitwith a grid of said electronicswitch for controlling current flow in said primary ignition circuit inresponse to current flow in the primary winding of said transformer anda voltage dividing network arranged to limit the voltage in the primarywinding to apredetermined maximum for limiting the negative potential onsaid grid.

4. In an ignition system of the character described for an internalcombustion engine wherein an electronic switch is used to control theflow of current from a D. C. source through a primary ignition circuit,the combination. comprising; an external load connectable to saidsource, a set of breaker points, a multitap resistance voltage divider,a transformer having primary connected with said breaker points and asecondary winding connected with said switch and means for selectivelyconnecting said primary with taps on said resistance for maintaining aconstant voltage across the primary winding when said load is connectedand disconnected with said source.

5. In an ignition system of the character described, the combinationcomprising, a source of D. C. current, an ignition coil and anelectronic switch having a variable potential grid arranged forcontrolling the flow ofcurrent between said source and coil, ameansincluding a transformer forchanging the potential of said grid,said transformer having a primary coil winding connectedwith said sourceand a set of breaker points and a secondaryconnected with said grid forcontrolling, current flow through said switch in response to currentflow changes in said primary winding and means connected between theprimary winding and the source for limitingthe voltage across theprimary winding to a predetermined value.

6. In an ignition system of the character described wherein anelectronic switch is used to control the flow fcurrent from a D. C.source to a primary ignition-circuit, the combination comprising; atransformer having a secondary winding connected with said switch and aprimary winding connected with said source and a means connected incircuit with said source and primary winding for limiting the voltage tosaid primary winding from said source and thereby to limit negativevoltagein said secondary circuit.

7. The combination as set forth in claim 4 wherein the external loadincludes a starting motor and the means which connects the primary coilof the transformer with the multi-tap resistance is operativelyconnected with a circuit which causesa starter'for the internalcombustion engine to be energized for increasing the current flowthrough said primary transformer coil whenever thesaid starter isenergized.

8. In an ignition system of the character described wherein anelectronic switch is used to control the flow of current from a D. C.source to a primary ignition circuit, the combination comprising; atransformer having a secondary winding connected with said switch andv aprimary winding connected with said source, and a means including amulti-tap resistance forv limiting and varying the source voltage tosaid primary winding to limit negative voltage in said-secondary.

9. In anignition system ofthe character described for an internalcombustionengine the combination-comprising a starting motor circuit forcranking said engine, .an electronic switch in control a flow of currentto a pri. mary ignition circuit,.a common D. C. current source for saidstarting-motor and sa-idprimary ignition circuit,,a

means to increase the current flow from said source to said primaryignition circuit and a means to increase the current flow from saidsource to a control circuit for said electronic switch during periodswhen said starting motor is energized by current from said source.

References Cited in the file of this patent UNITED STATES PATENTS ArthurJan. 26, 1932 Arthur May 1, 1934 Knight Oct. 10, 1939 Short et al. Jan.2, 1951 Short Apr. 24, 1951 Klei's Feb. 26, 1952

